The invention relates to a method and device for opening a valve, especially a load changing valve of an internal combustion engine.
From German patent 30 24 109 C2 a device, operating without camshaft, for actuating a load changing of an internal combustion engine is known. To the stem of the load changing valve an armature plate is fastened which in the fully open position of the valve contacts the solenoid and in the closed position of the valve contacts another solenoid. The armature plate forms together with the valve and two oppositely acting springs an oscillation system which upon activation of one solenoid is secured in one end position, whereby, upon switching off the solenoid, the armature plate moves toward the other end position and is secured thereat by activation of the other solenoid.
Such electromagnetic actuating devices, operating without camshaft, for the load changing valves of an internal combustion engine have the advantage that the control time can be selected substantially freely so that fuel consumption advantages can be achieved and the exhaust gas quality can be improved. A problem of such actuating devices is that the opening of the valve by pressure within the working chamber or combustion chamber is greatly impaired. For example, an exhaust valve must be opened already in certain operational phases when within the combustion chamber there is still a high working pressure. This high working pressure must be overcome by a spring which crowds the valve in the opening direction so that energy is removed from the oscillating system defined by the springs which energy must be then supplied by the solenoid. The solenoid which secures the valve in the fully open position must therefore be designed relatively large so that catching of the valve is possible. In the alternative, the springs must be so strong that high securing forces and thus large solenoids are required.
It is an object of the invention to provide a method and a device for opening a valve, especially a load changing valve of an internal combustion engine, with which a load changing valve can be opened safely and with minimal energy expenditure even when it must be opened counter to the excess pressure within the working chamber.